Pancreatic hormone (PP) [1] is a peptide synthesized in pancreatic islets of Langherhans, which acts as a regulator of pancreatic and gastrointestinal functions. A number of other active peptides are homologous to pancreatic hormone:

• Neuropeptide Y (NPY) [2], one of the most abundant peptides in the mammalian nervous system. NPY is implicated in the control of feeding and the secretion of the gonadotrophin-releasing hormone.
• Peptide YY (PYY) [3]. PPY is a gut peptide that inhibits exocrine pancreatic secretion, has a vasoconstrictory action and inhibits jejunal and colonic mobility.
• Various NPY and PYY-like polypeptides from fish and amphibians [4,5].
• Neuropeptide F (NPF) from invertebrates such as worms and snail [6].
• Skin peptide Tyr-Tyr (SPYY) from the frog Phyllomedusa bicolor. SPYY shows a large spectra of antibacterial and antifungal activity.

All these peptides are 36 to 39 amino acids long. Like most active peptides, their C-terminal is amidated and they are synthesized as larger protein precursors. The signature for these peptides is based on the last 17 C-terminal residues, where three positions are completely conserved. A profile was also developed that spans the whole peptide.